Resin Cement–Zirconia Bond Strengthening by Exposure to Low-Temperature Atmospheric Pressure Multi-Gas Plasma

The purpose of this study was to investigate the effect of gas species used for low-temperature atmospheric pressure plasma surface treatment, using various gas species and different treatment times, on zirconia surface state and the bond strength between zirconia and dental resin cement. Three groups of zirconia specimens with different surface treatments were prepared as follows: untreated group, alumina sandblasting treatment group, and plasma treatment group. Nitrogen (N2), carbon dioxide (CO2), oxygen (O2), argon (Ar), and air were employed for plasma irradiation. The bond strength between each zirconia specimen and resin cement was compared using a tension test. The effect of the gas species for plasma irradiation on the zirconia surface was investigated using a contact angle meter, an optical interferometer, an X-ray diffractometer, and X-ray photoelectric spectroscopy. Plasma irradiation increased the wettability and decreased the carbon contamination on the zirconia surface, whereas it did not affect the surface topography and crystalline phase. The bond strength varied depending on the gas species and irradiation time. Plasma treatment with N2 gas significantly increased bond strength compared to the untreated group and showed a high bond strength equivalent to that of the sandblasting treatment group. The removal of carbon contamination from the zirconia surface and an increase in the percentage of Zr-O2 on the zirconia surface by plasma irradiation might increase bond strength.

Enhanced thermoelectric performance of defect engineered monolayer graphene

We propose a method of improving the thermoelectric properties of graphene using defect engineering through plasma irradiation and atomic layer deposition (ALD). We intentionally created atomic blemishes in graphene by oxygen plasma treatment and subsequently healed the atomistically defective places using Pt-ALD. After healing, the thermal conductivity of the initially defective graphene increased slightly, while the electrical conductivity and the square of the Seebeck coefficient increased pronouncedly. The thermoelectric figure of merit of the Pt-ALD treated graphene was measured to be over 4.8 times higher than the values reported in the literature. We expect that our study could provide a useful guideline for the development of graphene-based thermoelectric devices.

INVESTIGATION OF TUNGSTEN SURFACE CARBIDIZATION UNDER PLASMA IRRADIATION

This paper presents the results of a study of the formation of a carbidized layer under various experimental conditions and the choice of optimal parameters for carbidization of a tungsten surface under plasma irradiation. To study the effect of the surface temperature of a tungsten sample and the duration of plasma irradiation, experiments were carried out at a sample surface temperature of 1300 °C and 1700 °C with an irradiation duration of 300–2400 s. Analysis of the research results showed that the maximum formation of W2C on the surface is observed at a test temperature of 1700 °C. At a temperature of 1300 °C, the phase composition of the carbidized layer depends on the duration of plasma irradiation. According to the literature analysis, the formation of WC occurs on the surface of tungsten, from which C diffuses into the particle and forms the underlying layer of W2C. With an increase in the ion fluence, depending on the irradiation time and the temperature of the sample surface, the diffusion of C into W accelerates, the WC content decreases, and W2C becomes the dominant carbide compound.

Effect of atmospheric-pressure plasma irradiation on the surface tension of water

We have shown that measuring the surface tension is a useful scheme to examine the plasma-liquid interface in real-time. The surface tension was measured using a method based on the dispersion relation of an acoustic capillary wave excited on the water surface. The surface tension gradually increased with time, when the water surface was irradiated with the outside region of the spatial afterglow of an atmospheric-pressure plasma. The Marangoni effect associated with the localized increase in the surface tension was observed during the plasma irradiation. The surface tension decreased after the termination of the discharge. A correlation was found between the transient decrease in the surface tension and the variation of the OH radical density in the gas phase. No increase in the surface tension was observed in the solution containing a trapping agent for liquid-phase OH radicals. These experimental results suggest that OH radicals act to increase the surface tension. However, the behavior of the surface tension cannot be explained perfectly by considering only the action of OH radicals.

Đánh giá bước đầu ứng dụng tia plasma lạnh trong điều trị hỗ trợ làm lành vết thương phần mềm trên bệnh nhân Covid-19 nặng

TÓM TẮT Đặt vấn đề: Plasma là môi trường chứa các vật chất không còn giữ được cấu trúc phân tử của mình mà bị ion hóa. Thể plasma lạnh được ứng dụng rộng rãi trong Y học với tính an toàn và hiệu quả được khẳng định trong nhiều nghiên cứu. Nghiên cứu này thực hiện tại Trung tâm Hồi sức Tích cực điều trị bệnh nhân COVID-19 của Bệnh viện Trung Ương Huế tại TP.Hồ Chí Minh nhằm mục đích (1) nhận định đặc điểm chung, đặc điểm lâm sàng của bệnh nhân COVID-19 nặng có sang thương phần mềm và (2) đánh giá bước đầu tác dụng tia plasma lạnh trong điều trị hỗ trợ làm lành vết thương phần mềm đối với bệnh nhân COVID-19 nặng Đối tượng, phương pháp: Khảo sát nhanh trong 45 ngày các bệnh nhân bị COVID-19 nặng có sang thương phần mềm đang điều trị tại Trung tâm Hồi sức Tích cực điều trị bệnh nhân COVID-19 trực thuộc Bệnh viện Trung Ương Huế tại TP.Hồ Chí Minh, nghiên cứu mô tả cắt ngang. Kết quả: Trong 915 bệnh nhân bị COVID-19 nặng, có 20 trường hợp bị thương tổn phần mềm được điều trị bằng chiếu tia Plasma lạnh, tỷ lệ nam, nữ 1 : 1, 70% nguyên nhân do loét ép độ I, II, III, 60% tổn thương vùng lưng, mông, cùng cụt. 55,0% thương tổn trước khi chuyển viện đến trung tâm. Sau 14 ngày điều trị 70% vết thương biểu mô hóa hoàn toàn, 90% hết rỉ dịch, sau 3 tuần tất cả vết thương hết đau, hết nổi mẫn hoàn toàn. Kết luận: Tia Plasma lạnh có vai trò tích cực trong hỗ trợ điều trị vết thương phần mềm đối với bệnh nhân COVID-19 mức độ nặng. ABSTRACT COLD PLASMA IRRADIATION AS AN ADJUVANT TREATMENT DIGITAL LESIONS FOR PATIENTS WITH SEVERE COVID-19: INITIAL EVALUATION Background: Plasma is a medium containing substances that no longer retain their molecular structure but are ionized. Cold plasma is widely used in medicine, with safety and effectiveness confirmed in many studies. This study was conducted at the Intensive Care Center for COVID-19 patients of Hue Central Hospital in Ho Chi Minh City to evaluate the general and clinical characteristics in severe COVID-19 patients with digital lesions, to evaluate the effect of cold plasma in the adjuvant treatment of soft tissue wound healing in patients with severe COVID-19 disease initially. Methods: This cross-section descriptive study was conducted on severe COVID-19 patients who undergo digital lesions treated at the COVID-19 Intensive Care Center operated by Hue Central Hospital in Ho Chi Minh, Vietnam, a quick 45 - day survey. Results: In 915 patients with severe COVID-19, 20 cases of digital lesions were experienced with cold plasma irradiation. The male - to - female ratio was 1: 1, 70% of wounds caused by pressure ulcers. 60% of lesions were located on the dorsum, gluteal and sacral region. 55.0% of lesions were discovered before transfer to our center. After 14 days of treatment, 70% of the wounds were completely epithelialized, 90% had no fluid oozing. After three weeks, all the lesions were pain-free, and the redness was completely terminated. Conclusion: Cold plasma Irradiation effectively supports the treatment of digital ulcers in patients with severe COVID-19 disease. Keywords: Cold plasma, COVID-19, pressure ulcers, dermatology, intensive care unit.

Study of the Temperature Dependence of a Carbidized Layer Formation on the Tungsten Surface Under Plasma Irradiation

The paper considers a method of tungsten surface carbidization using a beam-plasma discharge (BPD), which was implemented in a plasma-beam installation (PBI). The advantage of this method is to create conditions for chemical reactions and physical processes as close as possible to those possible in thermonuclear installations. The BPD makes it possible to generate plasma using different working gases. Methane was used as a plasma-forming gas. The working gas pressure in a chamber was (1,3-1,4)·10-1 Pa. The temperature dependence of the carbidized layer formation on the tungsten surface under plasma irradiation was determined in the temperature range of 700-1700 °C. The formation of tungsten carbides in surface layers was confirmed by SEM and X-ray diffraction analysis. It was found that interaction between tungsten and methane in a wide temperature range can proceed with simultaneous or sequential formation of the carbide phases W2C and WC.

Surface engineering of Ti3C2Tx MXene by oxygen plasma irradiation as room temperature ethanol sensor

In this work, a surface modification strategy by oxygen plasma irradiation was introduced for the first time to significantly improve the room temperature sensing performance of Ti3C2T[Formula: see text] MXene. Oxygen plasma irradiation induced TiO2 formation on the Ti3C2T[Formula: see text] surface, produced lattice distortion, increased the specific surface area, and provided mesoporous structures. The gas sensitivity performance characterization results show the gas response value of Ti3C2T[Formula: see text] irradiated for 0.5 h (Ti3C2T[Formula: see text]0.5P) was hundreds of times better than the pristine Ti3C2T[Formula: see text]alongside with its sufficient response time (280 s) and rapid recovery time (11 s). The excellent sensing performance is attributed to the formation of more reactive sites on the edge and basal planes of Ti3C2T[Formula: see text] and mesoporous structures which greatly improved the adsorption of ethanol. Additionally, the relatively low work function of TiO2 facilitates the formation of a Schottky junction for easy migration of charge carrier, the thereby shortening the sensing response time. This strategy offers a facile and controllable surface modification of other 2D materials, without damaging their structures.

Variations in Plant Growth Characteristics due to Oxygen Plasma Irradiation on Leaf and Seed

Gene expression variations of plant leaf are investigated by irradiating seed and leaf with oxygen or air plasmas. Enhancement of leaf growth is induced by oxygen plasma irradiation on seeds, which is supported by increased gene expression for protein synthesis, oxidative-reduction reactions and decreased gene expression concerning DNA methylation and histone modification. Suppression of leaf growth is observed by the oxygen plasma, which would be owing to increased gene expression concerning heat shock protein and redox reaction, and decreased expression of photosynthesis and glycoprotein. Also, gene expression variation due to air plasma irradiation is almost same as that of oxygen plasma. Active oxygen species are major factors in both oxygen and air plasmas for the variation of gene expressions in plant.

Deuterium retention in W-Ta alloys after low-temperature plasma irradiation and gas exposure

In this study plates of W, W-xTa alloys (x = 1; 3; 5 concentration in at.%) with a large grain size were used as experimental samples. All the samples were polished to a mirror surface and outgassed in vacuum at 1100 K during 2 hours. Sets of W, W-1Ta, W-3Ta, W-5Ta samples were irradiated with low-temperature D plasma up to fluences of 2e25 D/m2. Other sets of W, W-1Ta, W-3Ta, W-5Ta samples were exposed in D2 gas in a temperature range of 425625 K and pressure 103 Pa. The D retention in W and W-Ta alloys was measured by thermal desorption spectroscopy (TDS). An influence of Ta dopant on deuterium retention in W was observed. The dopant of tantalum slightly reduces the accumulation of deuterium in tungsten during gas exposure. Increasing temperature of samples during D-plasma irradiation from 415 K to 615 K reduces deuterium retention up to 2 orders of magnitude.